城墙、城壕、关隘这些古代用于军事防御的设施,早已成了历史的陈迹,但一些取义于古代城池的词语,如“固若金汤”“城隍”“城门失火,殃及池鱼”“阳关道”等,却沿用至今。为了弄清这些词语的来历,我们很有必要了解一些有关古代城池、关隘的常识。一、固若金汤我们形容一个城市设防严密、坚固,常用“固若金汤”这个成语。“固若 The ancient walls, moat, pass these ancient military defense facilities, has long been a historical monument, but some of the words taken from the ancient city, such as ”impregnable“ ”city “ ”gate fire, affecting the pool fish “Yang Road,” and so on, but still in use. In order to understand the origin of these words, we need to know some of the ancient city, pass the common sense. First, impregnable We describe a city fortified tight, strong, commonly used “impregnable” this idiom. "Solid if